Thermal stabilizers for jet fuels



United States Patent 3,323,884 THERMAL STABILIZERS FOR JET FUELS John W. Thompson and James C. Ownby, Kingsport,

Tenn, assignors to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey No Drawing. Original application Nov. 15, 1961, Ser. No. 152,642. Divided and this application June 15, 1965, Ser. No. 475,909

4 Claims. (Cl. 4466) This is a division of Ser. No. 152,642, filed Nov. 15, 1961 and now abandoned.

This invention relates to improved mineral oil compositions, more particularly to certain additives which improve thermal stability of hydrocarbon liquids, especially jet engine fuels.

Some jet airplane systems are now designed to employ fuel stored in the plane as a heat sink to absorb heat generated in operation of the aircraft. The fuel may be heated in the. tanks of the plane to high temperatures in the magnitude of 400-500 F. before it is ultimately consumed. Some jet fuels are unstable at these high temperatures. They deteriorate to form sludge which may clog fuel lines, filters and heat exchangers and may form harmful deposits in the engine.

A particular object of this invention is to provide jet engine fuels stabilized with certain additives that inhibit sludge formation at elevated temperatures. More generally an object is to provide certain additives for stabilizing liquid hydrocarbon fuels against deterioration at high temperatures. Another object is to provide new compounds useful as thermal stabilizers for hydrocarbon fuels, especially for jet engine fuels. The group of compounds which we have found suitable as additives for stabilizing jet fuels against high-temperature deterioration consists of certain N-acyl sarcosines and certain amide and diamide compounds which may be obtained by condensation of N-acyl sarcosines with certain amines and polyamines.

The N-acyl sarcosines which are effective stabilizers are those having the general formula:

wherein R represents an alkyl radical or alkenyl radical containing not less than 8 nor more than 18 carbon atoms. Specific examples of such compounds are N-pelargonyl sarcosine, N-lauroyl sarcosine, N-oleoyl sarcosine, and N- stearoyl sarcosine. N-oleoyl sarcosine is especially preferred. These compounds are available commercially.

Other compounds suitable for thermal stabilizers are amide derivatives of'N-acyl sarcosines which may be obtained by condensation of one mole of an N-acyl sarcosine with one mole of a monoamine or a polyamine in which only one amino group has available hydrogen. These amide derivatives are represented by the general formula:

0 R R- I lCH2 3N wherein R is the same as R defined above, R represents a hydrogen atom or alkyl radical and R" represents an alkyl, alkenyl, or alkylamino alkyl radical. In preferred embodiments, the total number of carbon atoms in R and R" does not exceed 24.

Preferred amines for preparing these derivatives may be primary alkyl amines, secondary dialkyl amines, or dialkyl amino alkyl amines. Examples of some typical amines that may be used for preparing these amide derivatives are methyl amine, dimethylamine, diethylamine, and dimethylaminopropylamine. Mixtures of amines of the type indicated are suitable for this purpose, for instance, a mixture and n represents a whole number 3,323,884 Patented June 6, 1967 of alkyl amines sold by Rohm and Haas Company known as Primene 8lR. This is essentially a mixture of primary alkyl amines in which the amino group is attached to a tertiary carbon atom of an alkyl group containing 18 to 24 carbon atoms per molecule. The condensation product will be a mixture of N-acyl sarcosine amides having the general formula above.

The following example illustrates a typical method for making the monoamide derivative of the invention.

Example 1 Equimolar amounts of N-oleoyl sarcosine and Primene 8l-R were mixed in a reaction flask equipped with a reflux condenser and a Dean-Stark trap. The mixture is then heated and refluxed at a temperature of 19026() F. until no further water collects in the trap. A slightly viscous, light-brown product remains in the flask. An acid number (ASTM D974) of only 17 indicates the product is essentially the amide condensation product.

Preferred among the stabilizing compounds provided according to this invention are the diamide derivatives of N-acyl sarcosines obtained by condensation of two moles of a N-acyl sarcosine with one mole of a poly(alkylamine). These diamide derivatives are represented by the general formula:

0 CH3 0 0 01130 H I II It I ll RCN-CHCNH[CH2CHzNH]..-CCH:NCR wherein R represents an alkyl or alkenyl radical containing not less than 8 nor more than 18 carbon atoms,

greater than zero.

Typical of the polyalkyleneamines which may be used as reactants to produce these diamide derivatives are ethylenediamine, diethylenetriamine, triethylenetetramine, and tetraethylene pentamine. Following is an example illustrating a preferred method for preparing the diamide derivative.

31.8 g. of N-oleoyl sarcosine and 8.4 g. of tetraethylene pentamine (2:1 molar ratio) are mixed in a reaction flask equipped as in Example 1. The mixture is heated and re fluxed at 178250 F. until no further water collects in the trap. The residue is a viscous brown liquid. Its acid number is only 1.9, indicating that the residue is essentially the diamide condensation product.

Ability of the stabilizer compounds of the invention to improve thermal stability of jet fuels was tested in the CFR (Cooperative Fuel Research) Fuel Coker.

The test is described in a paper by Crompton et al. titled Thermal Stability, A New Frontier for Jet Fuel and published in the Proceedings of the S.A.E. Summer Meeting in 1955. Instructions for operating the CFR Fuel Coker are in Manual No. 3 of Coordinating Research Council, Inc. Essentially the test is as follows:

Jet fuel is pumped at p.s.i. and at .aflow rate of 4-6 pounds per hour through a preheater, thence through a furnace where the fuel passes through a 20 micron, sintered stainless steel filter. In the preheater the fuel is heated to 300 400 F. and in the furnace to 400-500 F. Degradation products are deposited in the preheater and are also trapped on the filter where they eventually cause a pressure drop, which is measured across the filter by a manometer. The test continues until a pressure drop of 25 in. Hg is observed on the manometer, or until expiration of 300 minutes, whichever occurs first. Fuel stability is expressed in goodness units, an empirical function of observed pressure drop and test time. The scale of goodness units ranges from 0 for immediate clogging to 900 for no observed pressure drop within 300 minutes. At the end of the test the apparatus is disassembled and the preheater parts which were in contact with the fuel are examined for deposited material.

The fuels used to test the additives were JP4 and JP-S 4 vention may also be added to the fuel for other purposes, such as corrosion inhibitors, anti-icing agents, etc.

The invention has been described by reference to cerjet fuels. Specifications for these fuels may be found in tain preferred embodiments, it being understood that military specification Mil-14624 D and in ASTM D- 5 variations and modifications can be made within the scope 1655-59T. JP4 fuel is essentially a wide boiling range of the invention described above and defined 1n the folpetroleum fraction composed of about 35 volumes of kerolowing claims. sene and about 65 volumes of aviation gasoline. JP-S is We claim: a kerosene of high flash point (140 F.). Generally, jet 1. A fuel composition comprising a ma or proportlon fuels can be defined as light, non-viscous, low-flash-point of a liquid fuel, boiling in the aviation gasoline-kerosene products with a boiling range of about l405 10 F. These range, suitable for use as a jet engine fuel and a minor are clearly distinguished from lubricating oils, which have proportion of a thermal stabilizer additive selected from higher viscosity, flash-point, and boiling range. the group consisting of Fuels designated A, B and C were used in the (1) N-acyl sarcosine amide compounds represented test. Fuel A was composed of a mixture of several comby the general formula: mercially available JP-5 fuels, some stable at high tem- R, peratures and some unstable. Fuel B was JP-S fuel and if f Fuel C was a JP-4 fuel. RCNCHz-C-N Table I shows results of CFR Fuel Coker tests of fuels A, B, and C without additives and containing small amounts of some additives typical of the stabilizer addi wherein R represents a radical selected from the tives of the invention. group consisting of alkyl radicals and alkenyl radicals TABLE I Additive 0011- Test Fuel Deslg- Stabilizer Additive centration, Result Remarks nation Pounds per Goodness 1,000 Bbl. Units A N None A N-oleoyl sarcosine 2 60 25 838 A Amide product of condensation of N-oleoyl sarcosine with 2 80 Primene 81-11. 25 750 A Amide product of condensation of N-oleoyl sarcosine with 2 100 dimethylamine. A Amide product of condensation of N-oleoyl sarcosine with 2 93 dimethylarninopropylamine. 25 719 A Diamide product of condensation of N-oleoyl sarcosine with 2 160 diethylene-triamine. 5 365 A Diarnide product of condensation of N-oleoyl sarcosine with 2 708 tetraethylenepentarnine. 5 750 B None None 125 Diamide product of condensation of N-lauroyl sarcosine with 25 230 tetraethylenepentamine. None None 172 Diamide product of condensation of N-oleoyl sarcosine with 762 Noticed considerable reduction of deposit tetraethylenepentarnine. in preheater.

In the tests reported in Table I, for testing Fuel A, the preheater temperature was maintained at 400 F. and the temperature at the filter was 500 F. Fuels B and C were tested at preheater temperature of 300 F. and filter temperature of 400 F. The fuel flow rate for testing Fuel A was 6 lbs./ hr. and for testing Fuels B and C was 4 lbs/hr.

The concentration of additive necessary in the fuel to obtain the desired stability will depend upon the initial stability of the fuel being treated as well as upon the particular selected additive. In most cases a proportion somewhere between one lb. and 100 lbs. of stabilizer additive per 1000 bbl. of fuel will serve the purpose, but the optimum concentration will have to be determined for the individual case.

Selection of a particular stabilizer additive from the group provided by the invention will be largely an economic matter, depending upon relative costs of the compounds available and the amount of each required to achieve the desired degree of stabilization. As indicated by the data in Table I, different concentrations of the different stabilizers may be required to produce the same degree of thermal stability in a fuel. Smaller quantities of the diamide derivative of polyalkylamines are required to produce excellent stability. The N-oleoyl sarcosine derivatives are also preferred for the same reason.

For improving thermal stability of jet fuel and similar hydrocarbon fuels, any of the additives within the scope of the invention may be added to the fuel simply by mixing the oil and additive together by any suitable means.

Other additives which do not seriously interfere with the sludge inhibiting function of the additives of this inwhich contain from 8-18 carbon atoms, R represents a member selected from the group consisting of hydrogen atoms and alkyl radicals, and R" represents a member selected from the group consisting of alkyl, alkenyl and alkylaminoalkyl radicals and (2) N-acyl sarcosine diamide compounds represented by the general formula:

0 CH3 0 H I ll wherein R represents a radical selected from the group consisting of alkyl radicals and alkenyl radicals which contain from 8-18 carbon atoms, R represents a member selected from the group consisting of hydrogen atoms and alkyl radicals, and R" represents a member selected from the group consisting of alkyl, alkenyl and alkylaminoalkyl radicals and (I? CH3 C sented by (2) N-acyl sarcosine diamide compounds represented by the general formula:

wherein R is defined the same as above and n is 1-4. 5

3. A fuel composition consisting essentially of a liquid hydrocarbon fuel, boiling in the aviation gasolinekerosene range, suitable for use as a jet engine .fuel and from about 1 to about 100 pounds per 1000 barrels of said hydrocarbon fuel of a compound selected from the group consisting of compounds represented by the general formula:

0 CH3 0 R kerosine range, suitable for use as a jet engine fuel and from about 1 to about 100 pounds per 1000 barrels of said hydrocarbon fuel of a compound selected from the group consisting of compounds represented by the general formula:

consisting of alkyl radicals and alkenyl radicals which contain from 8-18 carbon atoms, and n is 14.

References Cited UNITED STATES PATENTS 4/1957 Spivack et al. 4466 X FOREIGN PATENTS l/1961 Canada.

OTHER REFERENCES Oil, Paint and Drug Reporter, 170 (14), page 40, Oct. 1, 1956.

DANIEL E. WYMAN, Primary Examiner. W. J. SHINE, Assistant Examiner. 

1. A FUEL COMPOSITION COMPRISING A MAJOR PROPORTION OF A LIQUID FUEL, BOILING IN THE AVIATION GASOLINE-KEROSENE RANGE, SUITABLE FOR USE AS A JET ENGINE FUEL AND A MINOR PROPORTION OF A THERMAL STABILIZER ADDITIVE SELECTED FROM THE GROUP CONSISTING OF (1) N-ACYL SARCOSINE AMIDE COMPOUNDS REPRESENTED BY THE GENERAL FORMULA: 